Removal of gaseous sulfur and phosphorus compounds by carbon-coated porous magnesium oxide composites

Chemical Engineering Journal 283 (2016) 1234–1243

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Chemical Engineering Journal
journal homepage: www.elsevier.com/locate/cej

Removal of gaseous sulfur and phosphorus compounds by carbon-coated
porous magnesium oxide composites
Anh-Tuan Vu a,b, Keon Ho a, Chang-Ha Lee a,⇑
a
b

Department of Chemical and Biomolecular Engineering, Yonsei University, Seoul, Republic of Korea
School of Chemical Engineering, Hanoi University of Science and Technology, Hanoi, Vietnam

h i g h l i g h t s

g r a p h i c a l a b s t r a c t

 Carbon-coated MgO composites were

synthesized using an aerogel method.
 MgO/C composites had a high surface

area of 723 m2/g.
 The sorption capacity of DMMP and

2-CEES was higher than those of MgO
and AC.
 The composite sorbed DMMP almost

twice more than 2-CEES in dry
condition.
 Carbon layer on MgO protected active
catalytic and sorption sites from H2O
molecules.

a r t i c l e

i n f o

Article history:
Received 1 June 2015
Received in revised form 31 July 2015
Accepted 1 August 2015
Available online 28 August 2015
Keywords:
MgO composite
Carbon
Aerogel
Sorption
2-CEES
DMMP

a b s t r a c t
Carbon-coated porous magnesium oxide (MgO/C) composites were synthesized using an aerogel route for
removal of dimethyl methylphosphonate (DMMP) and 2-chloroethyl ethyl sulfide (2-CEES) in dry and
wet conditions. The sorption capacities of the as-prepared samples for DMMP (0.23 lg/mL) and 2-CEES
(0.26 lg/mL) were evaluated by breakthrough experiments in nitrogen under ambient conditions.
MgO/C composites exhibited a decrease in surface area with carbon content (648–723 m2/g), but had a
higher surface area than MgO. Under dry conditions, the sorption capacities of the MgO/C composite with

a low carbon content of 6.39 wt% (MgO/C-1; 67.8 mg/g for DMMP and 35.3 mg/g for 2-CEES) were higher
than those of pure MgO and activated carbon (AC). The sorption capacity of MgO/C composites decreased
with an increase in carbon content and became even lower than those of MgO and AC. Under
humid conditions, the sorption capacities and breakthrough time of pure MgO decreased significantly
and became lower than that of AC. In contrast, the sorption capacities of the MgO/C-1 composite for
DMMP and 2-CEES under humid conditions remained at about 91 and 86% of those measured under
dry conditions, and were higher than those of AC. In addition, the MgO/C composite remained reactive
toward 2-CEES even under humid conditions. MgO/C composites were more stable than MgO under
humid conditions because of the presence of carbon-coated shells.
Ó 2015 Elsevier B.V. All rights reserved.

1. Introduction
Removal of hazardous chemicals from the environment is a critical issue from both biological and environmental standpoints
⇑ Corresponding author. Tel.: +82 02 2123 2762; fax: +82 02 312 6401.
E-mail address: (C.-H. Lee).
/>1385-8947/Ó 2015 Elsevier B.V. All rights reserved.

[1,2]. Environmental regulations for emissions from industries
and acceptable levels of human exposure are continuously being
adjusted and made more stringent.
The most abundant hazardous components can be classified
into two categories based on their source: natural and anthropogenic hazardous materials. Anthropogenic pollutants generally
originate from combustion, chemical reactions, or from the


A.-T. Vu et al. / Chemical Engineering Journal 283 (2016) 1234–1243

unsecured effluent of toxic materials. Furthermore, a considerable
amount of anthropogenic chemicals containing sulfur and phosphorus such as mustard, sarin, and soman agents are produced
for military purposes [3]. These anthropogenic chemicals are

highly persistent in the environment and critically harm humans
even at low concentrations.
Many efforts have been made both to reduce pollution and to
eliminate toxic materials from the environment. Adsorptive
removal of toxic components from the atmosphere is one of the
most attractive technologies [4].
Among various candidate solid materials, metal oxides have
been reported to be effective materials for adsorption and decomposition of toxic and persistent chemicals due to their high surface
areas, large number of highly reactive edges, corner defect sites,
unusual lattice planes, high surface-to-volume ratio, and reusability [5–11]. Particularly, magnesium oxide (MgO) materials have
been the focus of attention for decontamination of toxic chemicals
in recent years because well-designed MgO materials have a high
sorption capacity as well as effective decomposition ability.
Many studies have focused on methods to synthesize MgOs
with high surface area, pore volume, and small crystal size to
improve sorption capacity and reactivity for toxic chemicals
[12–15]. However, sorption capacity and reactivity of MgO are significantly reduced in the presence of water, because of the strong
affinity of MgO for water [6]. Furthermore, the excellent removal
performance of hazardous chemicals on adsorbents under dry conditions does not guarantee effectiveness in practice, because these
chemicals exist in the environment with a certain level of humidity. Even though many solid materials have been reported to have
higher efficiency under dry conditions than activated carbon, their
performance is often equivalent or worse than that of activated
carbon under humid conditions. Therefore, selection of solid
materials for the removal of hazardous chemicals under humid
conditions has been limited to strong hydrophilic adsorbents. It
would be highly desirable to design MgO-based composites
with hydrophobic surfaces that show high removal capacity for
hazardous chemicals under humid conditions.
Carbon-coated metal oxides have been produced using various
synthesis methods for various applications. A carbon-coated metal

oxide was developed to improve the stability, electric conductivity,
and electrochemical performance of batteries [16]. Coating of a
metal oxide with hydrophobic carbon could minimize the problem
of water adsorption because carbon has a non-polar surface [17]. In
addition, various carbon-coated metal oxides have been developed,
such as carbon-coated ZnO and CaO prepared by poly vinyl alcohol
pyrolysis [18], ferrite nanoparticles coated with carbon prepared
using a hydrothermal method [19], and carbon-coated Ni/TiO2
prepared via a hydrothermal method [20]. To create MgO/carbon
composites, various synthesis methods have been suggested,
including chemical vapor deposition (CVD), pyrolysis of a magnesium hydroxide aerogel modified with resorcinol, precipitation
with the assistance of sucrose, and one-pot assembly [17,21–23].
A chemical weapon agent (CWA) is a chemical substance whose
toxic properties are used to kill, injure, or incapacitate soldiers (and
sometimes civilians). Therefore, the decontamination of chemical
warfare agents is arguably the most challenging issue facing
militaries around the world. Furthermore, due to possible terror
threats, protecting civilians from CWAs has become increasingly
important for many governments.
Sulfur mustard (SM), commonly known as mustard gas, is a
class of related cytotoxic and vesicant CWAs, which can cause large
blistering on any exposed skin and in the lungs [24]. There is no
known antidote or specific treatment against SM exposure, and
the current therapy is largely supportive. Like some other nerve
CWAs, sarin attacks the nervous system by interfering with
the degradation of the neurotransmitter acetylcholine at

1235

neuromuscular junctions, and death will usually occur [25]. In various studies, dimethyl methylphosphonate (DMMP; CH3PO(OCH3)2)

is used as a simulant for toxic phosphorus compounds such as sarin
[26] and 2-chloroethyl ethyl sulfide (2-CEES; CH3CH2SCH2CH2Cl) is
often considered as a surrogate compound for SM [27,28].
Therefore, development of effective materials for removing DMMP
and 2-CEES could help protect the environment and humans from
refractory hazardous chemicals as well as CWAs.
In this study, carbon-coated magnesium oxide (MgO/C) composites were synthesized via an aerogel route to remove efficiently
CWAs. As representative surrogates of CWA, dimethyl methylphosphonate and 2-chloroethyl ethyl sulfide were selected. The
sorption capacities of the MgO/C composites were measured by
breakthrough experiments in gas phase under ambient dry and
wet conditions (0.23 and 0.26 lg/mL DMMP and 2-CEES in N2 flow,
respectively). The removal efficiency of the MgO/C composites
were evaluated and compared with those of pure MgO and
activated carbon (AC).

2. Experimental section
2.1. Materials
The following materials were used in this study: toluene
(Aldrich, USA, 99.9%), a magnesium methoxide solution in methanol (Aldrich, 7.82%), 2-CEES (Aldrich, 98%), DMMP (Aldrich, 97%),
glucose (Aldrich, 99%), activated carbon (Calgon Filtrasorb 300,
coal-derived AC), N2 gas (Dae-Deok Gas, Korea, 99.999%), H2
(Dae-Deok Gas, 99.999%), and air (Dae-Deok Gas, 99.999%). All
chemicals and solvents were used without further purification.

2.2. Preparation of composites
MgO/C composites were developed using an aerogel procedure.
In a typical experiment, which was conducted at room temperature, a mixture of toluene (100 mL) and magnesium methoxide
solution (20 mL) was placed in a glass reactor with a stirrer.
Another solution was prepared by dissolving the desired amount
of glucose in 2.0 mL of distilled water and this solution was slowly

added using a syringe to prepare the mixture. The addition of the
glucose solution led to a white cloudy precipitate, but the solution
became clear after a few minutes. To minimize evaporation of
organic solvent, the glass reactor top was covered with aluminum
foil. The mixture was stirred vigorously overnight at room temperature to allow completion of hydrolysis.
Subsequently, the hydrolysis gel was put into a high-pressure
autoclave reactor. The gel was first flushed and then pressurized
up to 100 psi with N2 gas. The autoclave reactor was gradually
heated from room temperature to 265 °C at a rate of 1.0 °C/min
and this temperature was remained for 10 min. Solvent vapors in
the reactor were quickly vented to the atmosphere and flushed
with N2 again to remove any remaining solvent vapors. The
obtained powder in the reactor was dried in an oven at 120 °C
for 12 h to remove residual organic solvents. Hydrated powder
(before calcination) was obtained and denoted HY-MgO/C.
The final step was calcination. Calcination has been shown to
improve the textural properties and sorption capacity of MgO
[12,29]. In this study, the hydrated powder was calcined in a
furnace under vacuum using the following steps to produce
mesoporous MgO with a high surface area: (1) ramping from room
temperature to 220 °C at 1 °C/min and soaking at 220 °C for 5 h, (2)
ramping from 220 to 280 °C at 0.8 °C/min and soaking at 280 °C for
1 h, (3) ramping from 280 to 350 °C at 0.8 °C/min and soaking at
350 °C for 2 h, and (4) ramping from 350 to 500 °C at 0.8 °C/min


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A.-T. Vu et al. / Chemical Engineering Journal 283 (2016) 1234–1243

and soaking at 500 °C for 5 h. The magnesium oxide/carbon
composite was obtained and stored in a glass bottle filled with N2.
In this study, to investigate the effect of the amount of carbon in
the MgO/C composites on their textural and physical properties as
well as sorption capacities, three different magnesium oxide/
carbon composites were prepared: molar ratios of magnesium
methoxide to glucose were 1:0.05, 1:0.09 and 1:0.18. The
as-prepared composites were denoted MgO/C-1, MgO/C-2, and
MgO/C-3, respectively. Activated carbon (AC) and pure MgO
(prepared using the same procedure to composite) were used for
comparison purposes.
2.3. Characterization
X-ray diffraction patterns (XRD) of as-synthesized samples
were recorded using an X-ray spectrometer (Ultima IV) using Cu
Ka radiation (k = 1.5418 ) operated at 40 kV and 100 mA, and
diffractograms were taken with a step size of 0.02°. XRD patterns
were recorded from 10° to 100° (2h) with a scanning step of
0.02°. X-ray photoelectron spectroscopy (XPS) was performed on
a Thermo VG using monochrome Al Ka as the excitation source.
Morphology and size of the samples were observed by transmission electron microcopy (TEM, JEM-2010), scanning electron
microscopy (SEM, Hitachi 4700), and energy-dispersive X-ray spectroscopy (EDS, JSM-7100F). Textural properties were measured by
N2 adsorption/desorption isotherms using a Quantachrome instrument (Autosorb iQ, version 3.0 analyzer). This instrument was also
used to measure the adsorption isotherms of water vapor for the
MgO and MgO/C samples. Fourier transform infrared spectroscopy
(FT-IR, VERTEX 70) was recorded in the wave range between 4000
and 400 cmÀ1.
2.4. Dynamic breakthrough experiments for removal of DMMP and
2-CEES
A schematic diagram of the dynamic breakthrough system is
shown in Fig. 1. A continuous flow column reactor (water-jacket

glass column), packed with as-prepared material, was used to measure the sorption capacities of the synthesized materials for DMMP
and 2-CEES at ambient. DMMP and 2-CEES vapors were generated
from a vessel in a water bath at 25 °C by nitrogen bubbling. Then,
the generated vapor was diluted by another N2 stream to control

experimental vapor concentration and prevent vapor condensation. Gas flows were controlled by two mass flow controllers
(MFCs). To confirm the homogeneous phase, the generated feed
gas was passed through a mixing tank. Before the breakthrough
experiments, the concentration of feed gas was confirmed by an
on-line gas chromatograph with a flame photometric detector
(GC; Agilent 6890N) through a by-pass line of the sorption column.
And the on-line GC was used to monitor the concentrations of
DMMP and 2-CEES at the outlet of the sorption column. Additionally, the components of outlet gas samples were analyzed by a
GC-MS (Agilent 7890A-5977A).
In each experiment, sorbent (50 mg) was packed into a waterjacket column reactor (inner diameter: 7 mm; length: 175 mm).
Then, glass beads and glass wool were put into both ends of the
column. The column temperature was controlled by a water circulator and measured by a thermocouple (RTD, Pt 100 X) inserted in
the column. Prior to sorption, the column was activated at 150 °C
with a pure N2 flow at 15 mL/min for 2 h, and then cooled to
25 °C. Subsequently, a mixture of DMMP or 2-CEES in N2 was fed
into the sorption column. The feed concentrations of DMMP and
2-CEES was calibrated before each breakthrough experiment and
controlled within the range of ±3%.
When sorbent particles are tested in a breakthrough experiment, differences in the pressure drop and bed porosity can result
in experimental deviations. Therefore, it is important to evaluate
materials using the same packing conditions as used in the breakthrough experiments [30–32]. In this study, an equal amount of
sample particles was packed into the column for each experiment.
The packing length occupied by the sorbent particles was also kept
equal in every experiment to maintain the same packing density.
Because the reactor was a glass column, the packing length could

be monitored during experiments. In addition, a low fixed flow rate
was used to minimize errors caused by changes in the packing
density (length) in breakthrough experiments even though the
experiments took longer.
Since the boiling point between 2-CEES and DMMP was different, it was not easy to carry out the breakthrough experiments
under the same flow rate and concentration. In the study, the
breakthrough experiments were carried out by using a similar concentration condition for each sorbate: DMMP (concentration;
0.23 lg/mL and flow rate; 30 mL/min) and 2-CEES (concentration;
0.26 lg/mL and flow rate; 22.5 mL/min) at 25 °C. Sorbent column

MFC: Mass Flow Controller
RTD: Resistance Temperature Detector

GC: Gas Chromatography
PG: Pressure Gauge

Fig. 1. Schematic diagram of breakthrough apparatus for DMMP and 2-CEES sorption.


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A.-T. Vu et al. / Chemical Engineering Journal 283 (2016) 1234–1243

pressure during the breakthrough experiments was measured by
two electrical pressure gauges. The pressure drop in all experiments was 0.25 psi due to packing sorbent particles. Breakthrough
saturation took a long time in each experiment due to dense
packing, the slow flow rate, and low concentrations of DMMP
and 2-CEES.
The sorption capacities of DMMP and 2-CEES were calculated
using the following equation:

F Â t0:5 Â C o
m  103

100
200
110

ð1Þ

AC

220
222

MgO/C-3

MgO/C-2

where F is the flow rate of the feed gas (mL/min), t0.5 is the time for
50% sorbate breakthrough (min), Co is the initial concentration of
DMMP or 2-CEES (lg/mL), and m is the sorbent mass (g).
The sorption equilibrium rate as well as sorbate breakthrough
can be used to quantify the dynamic sorption properties of
sorbents. The following Yoon and Nelson equation [33] was used
to fit the experimental breakthrough curves:

MgO/C-1

MgO

20

40

60

80

100

2-Theta (degree)



ð2Þ

The wide-angle XRD diffraction patterns of MgO, AC, and MgO/C
composites are presented in Fig. 2(a). Diffraction peaks were
observed at 2h values of 42.43, 61.78, and 77.73 corresponding to
the (2 0 0), (2 2 0), and (2 2 2) plans of MgO, respectively. This indicated that MgO had a cubic structure with a crystal lattice parameter of a = 4.21 Å (JCPDS No. 75-0447). In addition, the relatively
broad and low intensity of diffraction peaks indicated a small crystallite size of 4.1 nm approximated by using the Scherrer equation
[12], as presented in Table 1. Diffraction peaks were observed at
23.02, 43.40, and 79.24 of 2h values, which could be assigned to
crystal phase of commercial activated carbon (JCPDS No. 82-1691).
As shown in Fig. 2(a), all MgO/C composites exhibited the same
XRD diffraction peaks as MgO, but no characteristic peaks corresponding to carbon were detected, even though the carbon content
of the composites was as high as 17.86 wt% (MgO/C-3). We
deduced that the carbon in the composites was amorphous. The
intensity of diffraction peaks increased slightly with carbon content in the MgO/C composites. The crystallite size of the composites (2.8–3.1 nm) was smaller than that of MgO, as shown in
Table 1.

The chemical composition of the composites was determined
using X-ray photoelectron spectroscopy (XPS). As shown in Fig. 2
(b), full-scale XPS spectra of MgO and MgO/C composites exhibited
very clear MgO features. The photoelectron peaks at 49.8, 92.2, and
1304 eV corresponded to Mg 2p, 2s, and 1s, respectively, and the O
1s peak was at 553.0 eV, consistent with a previous report [34].
Activated carbon was obviously observed by the intense photoelectron peak C 1s at 284.6 eV. The peak was also observed with a
lower intensity than carbons in all the composites, indicating the
successful incorporation of carbon into MgO. The carbon content
in the composites estimated by the C 1s peak area was 6.39,
10.68, and 17.86 wt% for MgO/C-1, MgO/C-2, and MgO/C-3, respectively, as shown in Table 1. As expected, the carbon content

Mg KLL
C1s

AC

6

2.0x10

MgO

Mg2p

Mg2s

6

1.0x10

O2s

MgO/C-3

Mg KL5
KL3
Mg KL3
Mg KL1

O KL2
O KL1

1.5x10

C1s

6

3. Results and discussion
3.1. Characterization

O1s

C KL1

(b)

Mg1s

where KYN represents the Yoon–Nelson rate constant (minÀ1) and
t0.5 is the time for 50% sorbate breakthrough (min). The fit between
experimental data and Eq. (2) was found by determining the best
regression coefficient (R2) obtained with different couples (KYN,
t0.5). The value of t0.5 was used to evaluate the efficiency of the
sorbents.

6

2.5x10

Counts / s

ln


C
¼ K YN Â t À t0:5 Â K YN
Co À C

(a)

Intensity (a.u.)

Sorption capacity ðmg=gÞ ¼

002

MgO/C-2
5

5.0x10

MgO/C-1
0.0

1400

1200

1000

800

600

400

200

0

Binding Energy (eV)
Fig. 2. (a) XRD patterns and (b) XPS spectra of MgO, AC, MgO/C-1, MgO/C-2, and
MgO/C-3 samples.

increased with an increase in the amount of glucose used during
the synthesis.
N2 adsorption/desorption isotherms and pore size distributions
of MgO and MgO/C composites are presented in Fig. 3(a). BET surface area, pore volume, and the average pore size diameter of asprepared samples are presented in Table 1. The isotherm curve of

MgO was classified as a type IV based on the IUPAC system. In
addition, MgO had a sharp type H3 hysteresis loop containing a
steep region associated with closure of the hysteresis loop at the
relative pressure of $0.5. This suggested a mesoporous material
with non-rigid aggregated particles forming slit-shape pores. The
isotherm of AC was classified as type I, implying a microporous
material with a small average pore diameter (1.20 nm) in Table 1.
As shown in Fig. 3(a), the isotherm curves of the MgO/C
composites were type IV with a type H4 hysteresis loop at
P/Po = 0.4–1, showing a mesoporous material. The hysteresis loops
of composites were smaller than that of MgO and showed a shift of
the closure of hysteresis loop to a lower value. The results associated with narrow slit pores, including a pore in the micropore
region. Pore size distributions of composites were smaller than
that of MgO and were comparatively narrower with an average
pore diameter in the range of 3.43–3.84 nm.
When glucose and water were added into magnesium methoxide solution, the homogenous gels were formed because of the
interaction of glucose with Mg(OH) polymer-like gels by hydrogen


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A.-T. Vu et al. / Chemical Engineering Journal 283 (2016) 1234–1243

Table 1
Textural properties of MgO, MgO/C composites, and activated carbon.

a
b

Sample

BET surface
area (m2/g)

BJH mesopore
volume (cc/g)

SF microspore
volume (cc/g)

Total pore
volume (cc/g)

Average pore
diameter (nm)

Crystallite
sizea (nm)

wt% of
carbonb

MgO
HY-MgO/C-1
MgO/C-1
MgO/C-2
MgO/C-3
AC

512

1243
723
689
648
1336

1.62
2.33
1.36
1.30
1.14
0.461

0.146
0.259
0.444
0.434
0.451
0.459

1.766
2.589
1.804
1.734
1.591
0.920

5.66
3.64
3.84

3.43
3.43
1.20

4.1
–
2.8
2.9
3.1
–

–
–
6.39
10.68
17.86
–

Estimated by (2 0 0) XRD diffraction peak of MgO.
Result from XPS analysis.

6

1200

800

4
dV/dr (cc/g/nm)

Volume @ STP (cc/g)

1000

MgO/C-1
MgO/C-2
MgO/C-3
MgO
AC

(a)

5

3
2
1

600

0
0

5

10

400

15 20 25 30

Pore diameter (nm)

35

40

200
0

0.0

0.2

0.4

0.6

0.8

1.0

Relative pressure (P/Po)

(b)

MgO

Transmittance (%)

428

MgO/C-1
873
1637
1458
592

3440

4000

3500

3000

2500

2000

1500

1000

500

-1

Wavenumber (cm )
Fig. 3. (a) N2 isotherm curves (inset: pore size distribution) of AC, MgO, MgO/C-1,
MgO/C-2, and MgO/C-3 samples, (b) FTIR spectra of MgO and MgO/C-1 samples.

bonding or MgAO bonding [35,36] (Fig. S1). In addition, glucose
(melting temperature: 150 °C [37]) melted and spread out on the
surface of MgO during calcination. The glucose on the surface of
MgO resulted in improving the surface area and porosity of
composite. From the N2 sorption/desorption isotherms, the
MgO/C composites exhibited a high surface area and pore volume.
However, at high molar ratio of magnesium methoxide to glucose
(1:0.09 and 1:0.18), the precipitation was very significant and
the gels became less homogeneous. The extra carbon in the com-

posites led to a decrease in BET surface area as follows: MgO/C-1
(723 m2/g) > MgO/C-2 (689 m2/g) > MgO/C-3 (648 m2/g) > MgO
(512 m2/g) in Table 1. However, the surface areas of the composites
were smaller than those of AC and HY-MgO/C-1 (MgO/C-1 before
calcination). BJH mesopore volumes of composites (1.14–1.36 cc/g)
were smaller than that of MgO, but the SF micropore volumes
(0.434–0.451 cc/g) were higher than that of MgO. As mentioned
previously, the composites had well-developed mesopores and
some micropores. Even though the micropore volumes of the composites were similar to that of AC, the average pore diameter of the
composites was larger than that of AC. In addition, the surface
areas of the composites were much smaller than that of AC.
FT-IR spectra of MgO and MgO/C-1 as a representative composite are shown in Fig. 3(b). The spectra were similar to each other.
The broad intense band at 3440 cmÀ1 and minor peak at
1637 cmÀ1 were ascribed to stretching vibrations and bending
vibrations of (AOH) groups attached to the surfaces of particles
[38,39]. And these bands could be also ascribed to vibrational
stretching modes from (AOH) groups in adsorbed water molecules
[40]. The bands at the low frequencies of 873, 592, and 428 cmÀ1
were attributed to stretching vibrations of AMgAOAMgAOA

bonding. In addition, it was reported that the synthesized metal
oxides using metal alkoxides by an aerogel method contained a
certain number of (AOH) groups on the surface of the materials
[7]. And the band at 1458 cmÀ1 was ascribed to vibration of
MgAOH bonding [41,42]. These indicated that a number of AOH
groups from Mg(OH)2 remained on the surface of MgO and
MgO/C-1 particles despite calcination at 500 °C. However, no band
corresponding to MgAC, C@O, or CAH bonding was observed. This
once again implied that isolated carbon in amorphous phase
was formed after thermal decomposition of glucose in the
composites under vacuum at 500 °C.
TEM, SEM, and SEM/EDS images of MgO and MgO/C-1 samples
are shown in Fig. 4. Fig. 4(a) shows MgO bulk particles of
100–150 nm in size with a rough surface that formed due to aggregation of many small particles with about 4 nm in size, as shown in
Fig. 4(b), consistent with the XRD results presented in Table 1. The
morphology of the MgO/C-1 composite (Fig. 4(c)) was different
from that of MgO. The TEM image of MgO/C-1 in Fig. 4(d) showed
that amorphous carbon particles were well dispersed on the surface of the aggregated MgO particles and the particle were
$10 nm in size. In addition, the morphology of carbon could be
seen in the TEM images of MgO/C-1 sample after etching using
concentrated HCl, as shown in Fig. 4(e); many holes smaller than
5 nm were evident, but the particle sizes were similar to those of
MgO/C-1 before etching process. To further confirm the composition and structure of the composites, SEM/EDS measurements
were conducted on the MgO/C-1 sample. EDS spectrum results
for C, Mg, and O are shown in Fig. 4(f). The elemental map for C
shown in Fig. 4(g) indicated good distribution of C in the composite, while the map for Mg shown in Fig. 4(h) revealed aggregated
Mg. The SEM/EDS image shown in Fig. 4(i) revealed the absence


A.-T. Vu et al. / Chemical Engineering Journal 283 (2016) 1234–1243

1239

Fig. 4. SEM images of (a) MgO and (c) MgO/C-1; TEM images (b) MgO, (d) MgO/C-1, and (e) MgO/C-1 after etching MgO; (f) EDS spectrum of MgO/C-1; (g) and (h) elemental
maps of carbon and magnesium of MgO/C-1, respectively; (i) SEM/EDS image of MgO/C-1.

of the concentrated regions of specific elements; dispersion of carbon on the surface of MgO particles was the dominant finding. This
could be attributed to the interaction of glucose with the Mg(OH)2
polymer-like gels (Fig. S1) and the melting and spreading of glucose on the surface of MgO during calcination. Based on these
results, it was concluded that MgO was well coated by carbon,
resulting in core-shell structures. However, at high molar ratios
of magnesium methoxide to glucose, the carbon coated MgO particles could be mixed with extra carbons, which came from the additional amount of carbon source (glucose), as described above.
3.2. Removal of DMMP
Sorption behavior of as-prepared samples was determined by
breakthrough curves; the curves showed the DMMP concentration
at the outlet of the sorbent column as a function of time. Breakthrough curves for DMMP on MgO, activated carbon, and MgO/C
composites at 25 °C under dry conditions are shown in Fig. 5(a).
The breakthrough time of DMMP on MgO (199 min) was longer
than that of the MgO/C-2 and MgO/C-3 composites (164 and
129 min, respectively). However, the saturation time of MgO
(514 min) was shorter than that of MgO/C-2 and MgO/C-3 composites (589 and 534 min, respectively). Therefore, the breakthrough
shapes of MgO/C-2 and MgO/C-3 were a little wider than that of
MgO. In contrast, although there was not a significant difference
in breakthrough time between MgO/C-1 and MgO, the saturation
time of MgO/C-1 was much longer than that of MgO, MgO/C-2,
and MgO/C-3, as shown in Table 2. The breakthrough curve of
DMMP on activated carbon was steepest, while the breakthrough
and saturation times were shortest for the other samples even

though the activated carbon had a much higher surface area than

the other sorbents (see Table 1).
Since the molecular diameter of DMMP (0.57 nm) [43] is smaller than the pore size diameters of MgO, MgO/C composites, and
activated carbon, the DMMP molecules can penetrate into the
pores and sorb on the surface of the samples. And the sorption of
DMMP was attributed to physical sorption on active sites by MgAO
interaction [44], as shown in Fig. S2. Therefore, the surface area and
pore volume are the important factors that significantly contribute
to the sorption capacity of the sorbents. In regard to the surface
area and total pore volume, the sorption capacity of DMMP calculated from t0.5(exp) was as follows: MgO/C-1 (67.8 mg/g) > MgO/C-2
(43.7 mg/g) > MgO (42.2 mg/g) > MgO/C-3 (34.5 mg/g) > activated
carbon (30.4 mg/g). This clearly showed that sorption capacity
decreased with an increase in carbon content, and that it could
be considerably improved by coating MgO with a small amount
of carbon (MgO/C-1).
The breakthrough curve shape as well as slope can be affected
by sorption affinity and rate [30,32,45]. As shown in Fig. 5(a), activated carbon and as-prepared composites had different breakthrough curve shapes from one other. This can be explained by
the different affinities and concentration propagations of DMMP
on each sorbent material. It was reported that the molecular diameters of DMMP and 2-CEES were 0.57 and 0.69 nm, respectively
[43,46]. Considering the pore sizes of AC and MgO in Table 1, the
sorption affinity was a more important factor than mass transfer
resistance. The breakthrough curve slopes of all the composites
were wider than those of MgO and AC, and became steeper with
an increase in carbon content. This implied that the sorption affinity of DMMP on all the composites was weaker than those of MgO


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A.-T. Vu et al. / Chemical Engineering Journal 283 (2016) 1234–1243

1.0

(a)
0.8

C/Co

0.6

0.4

MgO/C-1
MgO/C-2
MgO/C-3
MgO
Activated carbon
Model

0.2

0.0
0

200

400

600

800

Time (min)

1.0

(b)
0.8

C/Co

0.6

0.4
MgO/C-1
MgO
Activated Carbon
Model

0.2

0.0
0

200

400

600

800

Time (min)
Fig. 5. Comparison of breakthrough curves for DMMP sorption on sorption column
packed by (a) MgO, MgO/C-1, MgO/C-2, MgO/C-3 or activated carbon in dry
condition, and (b) MgO, MgO/C-1 or activated carbon in humid condition (30 %RH).

and AC because the pore sizes of the composites were still larger
than that of AC. Since the difference in the pore sizes of all the composites was small, the increased sorption affinity of the composites
stemmed from increased carbon content and the sorption affinity
approached that of AC even though the sorption capacity
decreased. In addition, the Yoon–Nelson model could predict the
experimental breakthrough curves for all sorbents with R2 > 0.99.
The rate constants (KYN) obtained from model fitting were as

follows:
AC
(0.029 minÀ1) > MgO
(0.019 minÀ1) > MgO/C-3
À1
À1
(0.015 min ) > MgO/C-2 (0.014 min ) > MgO/C-1 (0.009 minÀ1).
Together, the results indicated that MgO/C composites prepared
using an aerogel method had improved BET surface area and
micropore volume than MgO. As carbon content in the composites
increased, the BET surface area and BJH mesopore volume
decreased. Sorption capacity with an increase in carbon content
was similar or smaller than that of MgO. The contribution of
improved surface area in the MgO/C composites to sorption capacity was limited. MgO/C-1 composite had the longest breakthrough
and saturation times as well as highest sorption capacity among
the as-prepared composites. MgO/C-1 was therefore selected for
further evaluation under humid conditions.

As mentioned previously, the fact that an as-prepared composite has a high removal capacity for toxic chemicals under dry conditions compared to MgO and AC is not sufficient for its practical
application, because toxic chemicals normally exist in humid conditions. To evaluate the effect of water vapor on the sorption of
DMMP, the removal efficiencies of MgO, MgO/C-1, and AC were
re-evaluated by using the feed gas of DMMP in N2 at a relative
humidity of 30% (30% RH). The other conditions for these breakthrough experiments under humid conditions were the same as
those used for experiments performed under dry conditions.
Breakthrough curves of DMMP on MgO, MgO/C-1, and activated
carbon at 30% RH are shown in Fig. 5(b). The breakthrough curve
shapes of all test sorbents were similar to those obtained under
dry conditions, but a reduction in the sorption capacity of MgO
was clearly observed.
The breakthrough and saturation times of MgO under humid
conditions (44 and 309 min, respectively) were much shorter than
those under dry conditions. As a result, sorption capacity under
humid conditions decreased significantly to 23.3 mg/g, corresponding to 56% of sorption capacity under dry conditions
(Table 2). We ascribed this to the sorption of water vapor on active
sites of MgO particles. The effect of humidity on sorption was not
significant for activated carbon. The rate constant, KYN
(0.035 minÀ1), increased under humid conditions, but breakthrough and saturation times decreased slightly. The relative
decrease in sorption capacity (24.6 mg/g) was much smaller than
that of MgO as shown in Table 2. As a result, the sorption capacity
of AC became similar to that of MgO, but the breakthrough time
was longer due to strong adsorption affinity under humid
conditions.
As expected from the AC results, the sorption of DMMP by
carbon-coated MgO (MgO/C-1) was not significantly affected by
the presence of water vapor. The breakthrough and saturation
times of DMMP for the MgO/C-1 sample were 179 and 744 min,
respectively, showing very little decrease in comparison with dry
conditions. Correspondingly, the sorption capacity under humid

conditions (61.5 mg/g) was 91% of that under dry conditions and
approximately 2.5-fold higher than those of activated carbon and
MgO under humid conditions. In addition, the rate constant (KYN)

Table 2
Breakthrough and saturation times, and sorption capacity of DMMP in dry and humid condition (30 %RH).
Sample

Condition

tb (min)

ts (min)

t0.5 (fit)

t0.5 (exp)

KYN (minÀ1)

R2

Sorption capacity (mg/g)

AC
MgO
MgO/C-1
MgO/C-2
MgO/C-3
AC

MgO
MgO/C-1

Dry
Dry
Dry
Dry
Dry
Humid
Humid
Humid

159
199
189
164
129
139
39
179

369
514
784
589
534
344
309
744

224
312
493
330
250
186
166
444

221
306
491
317
243
179
169
446

0.029
0.019
0.009
0.014
0.015
0.035
0.016
0.010

0.996
0.998
0.990

0.997
0.993
0.990
0.994
0.992

30.4
42.2
67.8
43.7
34.5
24.6
23.3
61.5

tb and ts are breakthrough and saturation times, respectively.
t0.5 (fit) and t0.5 (exp) are the times for 50% sorbate breakthrough obtained from fitting and interpolation for experimental data, respectively.


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A.-T. Vu et al. / Chemical Engineering Journal 283 (2016) 1234–1243

The result is also supported by the water adsorption isotherms
shown in Fig. 7. The interaction sorption capacity of MgO with
water vapor was much stronger and larger than that of the
MgO/C-1 composite. This implied that the hydrophobicity of the
carbon shell effectively protected the MgO crystals from water
vapor.

200

Mg(OH)2

Intensity (a.u.)

220

(d)

222

3.3. Removal of 2-CEES

Mg(OH)2

(b)

(a)
20

40

60

80

100

2-Theta (degree)

Fig. 6. XRD patterns before and after DMMP sorption in humid condition,
respectively: (a) and (b) for MgO, and (c) and (d) for MgO/C-1.

under humid conditions was also similar to that under dry conditions, as shown in Table 2. MgO and the MgO/C-1 composite
showed different behaviors for sorption of DMMP according to
the presence of water vapor. The breakthrough and saturation
times as well as sorption capacity of MgO were significantly lower
than those obtained under dry conditions, while these values did
not differ much for the MgO/C-1 composite. Therefore, a carboncoated MgO composite was successfully developed to remove
DMMP efficiently under both dry and humid conditions.
To investigate the effect of water vapor on the crystalline structure of MgO and the MgO/C-1 composite, both sorbents were analyzed by XRD after DMMP sorption under humid conditions. The
XRD patterns before and after sorption are compared in Fig. 6.
No significant changes in the peak intensity, full width at half maximum (FWHM), or peak position of (2 0 0), (2 2 0), and (2 2 2) crystal
plans of either sorbent was observed after DMMP sorption under
humid conditions. MgO underwent substantial conversion to Mg
(OH)2 crystallite, leading to the appearance of Mg(OH)2 diffraction
peaks. This was due to the reaction of MgO with water. In contrast,
no significant diffraction peaks of Mg(OH)2 were observed for the
MgO/C-1 composite. This implied that it was difficult for MgO to
react with water molecules in the composite.

Identical breakthrough experiments as performed with DMMP
were carried out for the feed gas of 2-CEES (0.26 lg/mL) in N2 at
22.5 mL/min. The breakthrough curves of 2-CEES on the MgO and
MgO/C-1 sorbents under dry conditions are presented in Fig. 8
(a). Each sorbent had two breakthrough curves: a 2-CEES curve
and a reacted product curve. The composition of outlet gas from
the breakthrough column for 2-CEES sorption was analyzed by a
GC-MS. Vinyl ethyl sulfide (CH3CH2SCH@CH2) and 2-CEES were
detected at 6.7 and 12.2 min of retention times, respectively, as

shown in Fig. S3. The sorption and decomposition of 2-CEES on sorbents result from the reactive site of the isolated (AOH) groups
(Fig. S4). Breakthrough times, saturation times, and sorption capacities are listed in Table 3.

1.0

2-CEES/MgO
product/MgO
2-CEES/MgO/C-1
product/MgO/C-1
model

0.8

0.6

0.4

0.2

0.0
0

100

200

300

400

500

Time (min)

1.0

2-CEES/MgO
2-CEES/MgO/C-1
product/MgO/C-1
model

900
800

(a)

C/Co

(c)

MgO/C-1
MgO

0.8

(b)

0.6

600

C/Co

Volume @ STP (cc/g)

700

500

0.4
400
300

0.2
200
100

0.0
0

0

0.0

0.2

0.4

0.6

0.8

Relative pressure (P/Po)
Fig. 7. Water vapor adsorption isotherms of MgO and MgO/C-1.

1.0

100

200

300

400

Time (min)
Fig. 8. Comparison of breakthrough curves for 2-CEES sorption on sorption column
packed by (a) MgO and MgO/C-1 in dry condition, and (b) MgO and MgO/C-1 in
humid condition (39 %RH).


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A.-T. Vu et al. / Chemical Engineering Journal 283 (2016) 1234–1243

Table 3
Breakthrough and saturation times, and sorption capacity of 2-CEES in dry and humid condition (39 %RH).
Sample

Condition

tb (min)

ts (min)

t0.5 (fit)

t0.5 (exp)

KYN (minÀ1)

R2

Sorption capacity (mg/g)

MgO
MgO/C-1
MgO
MgO/C-1

Dry
Dry
Humid
Humid

202
222
42
152

392
397
297
327

290
305
194
262

288
302
190
260

0.035
0.036
0.025
0.049

0.994
0.998
0.996
0.999

33.7
35.3
22.2
30.4

tb and ts are breakthrough and saturation times, respectively.
t0.5 (fit) and t0.5 (exp) are the times for 50% sorbate breakthrough obtained from fitting and interpolation for experimental data, respectively.

The breakthrough curve shapes of 2-CEES on MgO and the MgO/
C-1 composite were similar with a rate constant (KYN) of 0.035 and
0.036 minÀ1, respectively. The breakthrough time, saturation time,
and sorption capacity of 2-CEES on MgO was 202 min, 392 min,
and 33.7 mg/g, respectively. The corresponding values for the
MgO/C-1 composite (222 min, 397 min, and 35.3 mg/g) were
slightly higher than those of MgO, as shown in Table 3. Compared
to the results obtained for DMMP, the sorption rate constant was
faster, but the saturated sorption amount was smaller.
In view of the reactivity shown in Fig. 8(a), decomposition of
2-CEES on MgO was greater than of the MgO/C-1 composite. The
reacted product appeared before 2-CEES breakthrough in MgO,
but the reacted product took much longer to appear for the MgO/
C-1 sample due to penetration of 2-CEES and product molecules
into the carbon-coated shells of the composite particles. As mentioned in Fig. 3(b), it was again confirmed that (-OH) groups
remained on the surface of MgO and that these groups played a
role in the reaction of 2-CEES with MgO [6,11,47,48]. The reaction
could be explained by the following equation:

ðOHÞAMgOA þ CH2 ClACHASACH2 ACH3
! ClAMgOA þ CH2 @CHASACH2 ACH3 þ H2 O

ð3Þ

The sorption and reaction of 2-CEES on MgO and MgO/C-1 composites in the presence of water vapor (39% RH) are shown in Fig. 8
(b). The breakthrough shape of 2-CEES on MgO was wider with a
decreased rate constant (KYN) of 0.025 minÀ1, implying that the

sorption affinity of 2-CEES for MgO was significantly lower under
humid conditions than dry conditions. The breakthrough and saturation times of 2-CEES on MgO under humid conditions also
decreased steeply to 42 and 297 min, respectively. As a result,
the sorption capacity was 22.2 mg/g and the change in sorption
behavior under humid conditions was the same as that obtained
for DMMP, as shown in Tables 2 and 3. Furthermore, no reacted
product was observed owing to sorption of water molecules on catalytic active sites of MgO.
In contrast, the breakthrough shape of the MgO/C-1 composite
became steeper with a higher rate constant (KYN) of 0.049 minÀ1
than that obtained under dry conditions. The breakthrough and
saturation times of the MgO/C-1 composite were 152 and
324 min, respectively, representing a smaller decrease than seen
for MgO. The sorption capacity of the composite under humid conditions was about 86% of that under dry conditions, and was much
larger than that of MgO, as shown in Table 3. Furthermore, for the
MgO/C-1 composite, vinyl ethyl sulfide from the reaction of 2-CEES
with MgO was still detected, although levels of this product concentration were lower than that obtained under dry conditions.
High sorption capacity and reactivity of 2-CEES on the MgO/C-1
composite under humid conditions confirmed again that the carbon in the MgO/C composite worked as a hydrophobic shell and
protected MgO from water sorption.
4. Conclusions
Carbon-coated MgO composites were prepared via an aerogel
route with glucose as a carbon precursor to efficiently remove

2-CEES and DMMP. MgO/C composites had higher surface areas
and microspore volumes and lower mesopore volumes and crystallite sizes than MgO. As the glucose amount in the synthesis step
increased, the carbon content of the MgO/C composites increased
and the surface area and mesopore volume decreased because
too much amount of glucose addition led to forming carbon out
of the surface of MgO. The MgO/C composite with 6.39 wt% carbon
showed the highest sorption capacity for DMMP (67.8 mg/g at

0.23 lg/mL) and 2-CEES (35.3 mg/g at 0.26 lg/mL) among the assynthesized composites under dry conditions. The sorption capacities of MgO and the MgO/C composites were higher than that of
AC, even though the surface area of AC was the highest. In addition,
the sorption capacity of MgO/C composites decreased with an
increase in carbon content. MgO/C composites with more than
10 wt% carbon had lower sorption capacity than MgO, even though
their surface areas were larger than that of MgO. This implied that
the contribution of the surface area to sorption capacity was limited, but the sorption affinity played an important role in determining sorption capacity.
Under humid conditions, the sorption capacities of DMMP and
2-CEES on MgO decreased significantly. Furthermore, MgO lost
reactivity toward 2-CEES due to the sorption of water molecule
on catalytic active sites. In contrast, carbon content of the composite allowed effective protection of sorption and reaction of DMMP
and 2-CEES from water vapor. The sorption capacities of DMMP
and 2-CEES on the MgO/C-1 sample under humid conditions were
61.5 mg/g and 30.4 mg/g, about 91% and 86% of those under dry
conditions, respectively. The carbon shell protected the sorbent
composite from water vapor. Because aerogel MgO with higher
mesopore volume than AC can have a higher sorption affinity
and capacity for CWA molecules than AC, a carbon thin layer coating of MgO is the most promising way to produce the sorbents with
higher sorption capacity and reactivity than AC in humid condition.
Acknowledgements
We would like to acknowledge the financial support from the
R&D Convergence Program of MSIP (Ministry of Science, ICT and
Future Planning) and NST (National Research Council of Science
& Technology) of Republic of Korea (CRC-14-1-KRICT).
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at />References
[1] E. Barea, C. Montoro, J.A.R. Navarro, Toxic gas removal–metal–organic
frameworks for the capture and degradation of toxic gases and vapours,
Chem. Soc. Rev. 43 (2014) 5419–5430.

[2] Y. Safa, H.N. Bhatti, Adsorptive removal of direct textile dyes by low cost
agricultural waste: application of factorial design analysis, Chem. Eng. J. 167
(2011) 35–41.
[3] Y.C. Yang, J.A. Baker, J.R. Ward, Decontamination of chemical warfare agents,
Chem. Rev. 92 (1992) 1729–1743.


A.-T. Vu et al. / Chemical Engineering Journal 283 (2016) 1234–1243
[4] N.A. Khan, Z. Hasan, S.H. Jhung, Adsorptive removal of hazardous materials
using metal-organic frameworks (MOFs): a review, J. Hazard. Mater. 244–245
(2013) 444–456.
[5] A. Kleinhammes, G.W. Wagner, H. Kulkarni, Y. Jia, Q. Zhang, L.-C. Qin, Y. Wu,
Decontamination of 2-chloroethyl ethylsulfide using titanate nanoscrolls,
Chem. Phys. Lett. 411 (2005) 81–85.
[6] R.M. Narske, K.J. Klabunde, S. Fultz, Solvent effects on the heterogeneous
adsorption and reactions of (2-chloroethyl)ethyl sulfide on nanocrystalline
magnesium oxide, Langmuir 18 (2002) 4819–4825.
[7] M.E. Martin, R.M. Narske, K.J. Klabunde, Mesoporous metal oxides formed by
aggregation of nanocrystals. Behavior of aluminum oxide and mixtures
with magnesium oxide in destructive adsorption of the chemical warfare
surrogate 2-chloroethylethyl sulfide, Microporous Mesoporous Mater. 83
(2005) 47–50.
[8] G.W. Wagner, O.B. Koper, E. Lucas, S. Decker, K.J. Klabunde, Reactions of VX,
GD, and HD with nanosize CaO: autocatalytic dehydrohalogenation of HD, J.
Phys. Chem. B 104 (2000) 5118–5123.
[9] K.J. Klabunde, J. Stark, O. Koper, C. Mohs, D.G. Park, S. Decker, Y. Jiang, I.
Lagadic, D. Zhang, Nanocrystals as stoichiometric reagents with unique surface
chemistry, J. Phys. Chem. 100 (1996) 12142–12153.
[10] B.W.L. Jang, J.J. Spivey, Catalytic hydrodesulfurization and hydrodechlorination
of chloroethyl ethyl sulfide, Catal. Today 55 (2000) 3–10.

[11] A.-T. Vu, S. Jiang, K. Ho, J.B. Lee, C.-H. Lee, Mesoporous magnesium oxide and
its composites: preparation, characterization, and removal of 2-chloroethyl
ethyl sulfide, Chem. Eng. J. 269 (2015) 82–93.
[12] A.-T. Vu, S. Jiang, Y.-H. Kim, C.-H. Lee, Controlling the physical properties of
magnesium oxide using a calcination method in aerogel synthesis: its
application to enhanced sorption of a sulfur compound, Ind. Eng. Chem. Res.
53 (2014) 13228–13235.
[13] Y.-H. Kim, V.A. Tuan, M.-K. Park, C.-H. Lee, Sulfur removal from municipal gas
using magnesium oxides and a magnesium oxide/silicon dioxide composite,
Microporous Mesoporous Mater. 197 (2014) 299–307.
[14] Y. Ding, G. Zhang, H. Wu, B. Hai, L. Wang, Y. Qian, Nanoscale magnesium
hydroxide and magnesium oxide powders: control over size, shape, and
structure via hydrothermal synthesis, Chem. Mater. 13 (2001) 435–440.
[15] G. Moussavi, M. Mahmoudi, Degradation and biodegradability improvement of
the reactive red 198 azo dye using catalytic ozonation with MgO nanocrystals,
Chem. Eng. J. 152 (2009) 1–7.
[16] X. Liu, N. Bi, C. Feng, S.W. Or, Y. Sun, C. Jin, W. Li, F. Xiao, Onion-like carbon
coated CuO nanocapsules: a highly reversible anode material for lithium ion
batteries, J. Alloys Compd. 587 (2014) 1–5.
[17] A.F. Bedilo, M.J. Sigel, O.B. Koper, M.S. Melgunov, K.J. Klabunde, Synthesis
of carbon-coated MgO nanoparticles, J. Mater. Chem. 12 (2002)
3599–3604.
[18] B. Özkal, W. Jiang, O. Yamamoto, K. Fuda, Z.-E. Nakagawa, Preparation and
characterization of carbon-coated ZnO and CaO powders by pyrolysis of PVA, J.
Mater. Sci. 42 (2007) 983–988.
[19] H. Bae, T. Ahmad, I. Rhee, Y. Chang, S.-U. Jin, S. Hong, Carbon-coated iron oxide
nanoparticles as contrast agents in magnetic resonance imaging, Nanoscale
Res. Lett. 7 (2012) 1–5.
[20] W. Lin, H. Cheng, J. Ming, Y. Yu, F. Zhao, Deactivation of Ni/TiO2 catalyst in the
hydrogenation of nitrobenzene in water and improvement in its stability by

coating a layer of hydrophobic carbon, J. Catal. 291 (2012) 149–154.
[21] M.S. Mel’gunov, E.A. Mel’gunova, V.I. Zaikovskii, V.B. Fenelonov, A.F. Bedilo, K.J.
Klabunde, Carbon dispersion and morphology in carbon-coated
nanocrystalline MgO, Langmuir 19 (2003) 10426–10433.
[22] Q. Zhou, J.-W. Yang, Y.-Z. Wang, Y.-H. Wu, D.-Z. Wang, Preparation of nanoMgO/carbon composites from sucrose-assisted synthesis for highly efficient
dehydrochlorination process, Mater. Lett. 62 (2008) 1887–1889.
[23] L. She, J. Li, Y. Wan, X. Yao, B. Tu, D. Zhao, Synthesis of ordered mesoporous
MgO/carbon composites by a one-pot assembly of amphiphilic triblock
copolymers, J. Mater. Chem. 21 (2011) 795–800.
[24] S.C. Stout, S.C. Larsen, V.H. Grassian, Adsorption, desorption and thermal
oxidation of 2-CEES on nanocrystalline zeolites, Microporous Mesoporous
Mater. 100 (2007) 77–86.
[25] L.L. Chao, S. Kriger, S. Buckley, P. Ng, S.G. Mueller, Effects of low-level sarin and
cyclosarin exposure on hippocampal subfields in Gulf War Veterans,
NeuroToxicology 44 (2014) 263–269.
[26] J. Quenneville, R.S. Taylor, A.C.T. van Duin, Reactive molecular dynamics
studies of DMMP adsorption and reactivity on amorphous silica surfaces, J.
Phys. Chem. C 114 (2010) 18894–18902.

1243

[27] C.W. Kanyi, D.C. Doetschman, J.T. Schulte, Nucleophilic chemistry of X-type
Faujasite zeolites with 2-chloroethyl ethyl sulfide (CEES), a simulant of
common mustard gas, Microporous Mesoporous Mater. 124 (2009) 232–235.
[28] J.A. Arcibar-Orozco, T.J. Bandosz, Visible light enhanced removal of a sulfur
mustard gas surrogate from a vapor phase on novel hydrous ferric
oxide/graphite oxide composites, J. Mater. Chem. A 3 (2015) 220–231.
[29] A.-T. Vu, Y. Park, P.R. Jeon, C.-H. Lee, Mesoporous MgO sorbent promoted with
KNO3 for CO2 capture at intermediate temperatures, Chem. Eng. J. 258 (2014)
254–264.

[30] S.-H. Lim, E.-J. Woo, H. Lee, C.-H. Lee, Synthesis of magnetite–mesoporous
silica composites as adsorbents for desulfurization from natural gas, Appl.
Catal. B 85 (2008) 71–76.
[31] J.-M. Kwon, J.-H. Moon, Y.-S. Bae, D.-G. Lee, H.-C. Sohn, C.-H. Lee, Adsorptive
desulfurization and denitrogenation of refinery fuels using mesoporous silica
adsorbents, ChemSusChem 1 (2008) 307–309.
[32] A. Koriakin, Y.-H. Kim, C.-H. Lee, Adsorptive desulfurization of natural gas
using lithium-modified mesoporous silica, Ind. Eng. Chem. Res. 51 (2012)
14489–14495.
[33] Y.H. Yoon, J.H. Nelson, Application of gas adsorption kinetics – II. A theoretical
model for respirator cartridge service life and its practical applications, Am.
Indian Hygiene Assoc. J. 45 (1984) 517–524.
[34] M.-H. Oh, K.-W. Kim, S. Choi, R.K. Singh, Preparation of monodispersed
magnesia coated silica particles through a surface-induced precipitation
method, Powder Technol. 204 (2010) 154–158.
[35] J. Liu, T.-H. Bae, O. Esekhile, S. Nair, C. Jones, W. Koros, Formation of Mg(OH)2
nanowhiskers on LTA zeolite surfaces using a sol–gel method, J. Sol–Gel. Sci.
Technol. 60 (2011) 189–197.
[36] C. Trionfetti, I.V. Babich, K. Seshan, L. Lefferts, Formation of high surface area
Li/MgO—efficient catalyst for the oxidative dehydrogenation/cracking of
propane, Appl. Catal. A 310 (2006) 105–113.
[37] J.W. Lee, L.C. Thomas, S.J. Schmidt, Can the thermodynamic melting
temperature of sucrose, glucose, and fructose be measured using rapidscanning differential scanning calorimetry (DSC), J. Agric. Food Chem. 59
(2011) 3306–3310.
[38] Y. Diao, W.P. Walawender, C.M. Sorensen, K.J. Klabunde, T. Ricker, Hydrolysis
of magnesium methoxide. Effects of toluene on gel structure and gel
chemistry, Chem. Mater. 14 (2002) 362–368.
[39] J. Zhou, S. Yang, J. Yu, Facile fabrication of mesoporous MgO microspheres and
their enhanced adsorption performance for phosphate from aqueous solutions,
Colloids Surf. A 379 (2011) 102–108.

[40] R. Trujillano, E. Rico, M.A. Vicente, M. Herrero, V. Rives, Microwave radiation
and mechanical grinding as new ways for preparation of saponite-like
materials, Appl. Clay Sci. 48 (2010) 32–38.
[41] D. Hassouna, C. Hedia, T. Fathi, Mg(OH)2 nanorods synthesized by A facile
hydrothermal method in the presence of CTAB, Nano-Micro Lett. 3 (2011)
153–159.
[42] X. Wu, H. Cao, G. Yin, J. Yin, Y. Lu, B. Li, MgCO3Á3H2O and MgO complex
nanostructures: controllable biomimetic fabrication and physical chemical
properties, Phys. Chem. Chem. Phys. 13 (2011) 5047–5052.
[43] X. Lu, V. Nguyen, X. Zeng, B.J. Elliott, D.L. Gin, Selective rejection of a
water-soluble nerve agent stimulant using a nanoporous lyotropic liquid
crystal–butyl rubber vapor barrier material: evidence for a molecular sizediscrimination mechanism, J. Membr. Sci. 318 (2008) 397–404.
[44] Y.X. Li, O. Koper, M. Atteya, K.J. Klabunde, Adsorption and decomposition of
organophosphorus compounds on nanoscale metal oxide particles. In situ GCMS studies of pulsed microreactions over magnesium oxide, Chem. Mater. 4
(1992) 323–330.
[45] A. Ryzhikov, V. Hulea, D. Tichit, C. Leroi, D. Anglerot, B. Coq, P. Trens, Methyl
mercaptan and carbonyl sulfide traces removal through adsorption and
catalysis on zeolites and layered double hydroxides, Appl. Catal. A 397
(2011) 218–224.
[46] A. Roy, A.K. Srivastava, B. Singh, D. Shah, T.H. Mahato, A. Srivastava, Kinetics of
degradation of sulfur mustard and sarin simulants on HKUST-1 metal organic
framework, Dalton Trans. 41 (2012) 12346–12348.
[47] D.B. Mawhinney, J.A. Rossin, K. Gerhart, J.T. Yates, Adsorption and reaction
of 2-chloroethylethyl sulfide with Al2O3 surfaces, Langmuir 15 (1999)
4789–4795.
[48] D.A. Giannakoudakis, J.A. Arcibar-Orozco, T.J. Bandosz, Key role of terminal
hydroxyl groups and visible light in the reactive adsorption/catalytic
conversion of mustard gas surrogate on zinc (hydr)oxides, Appl. Catal. B
174–175 (2015) 96–104.